Friction Drive Conveyor Assembly

ABSTRACT

An overhead mounted friction drive conveyor assembly including a biasing section for biasing objects such as car doors. The conveyor assembly includes a conveying rail and a biasing rail extending in spaced and parallel relationship with the conveying rail. The conveyor assembly also includes at least three trolleys and at least two tow bars extending between and interconnecting the trolleys. A biasing mechanism allows at least two of the trolleys to remain on the conveying rail and guides at least one trolley onto the biasing rail so that one of the tow bars extends between the biasing rails. The object is disposed on the tow bar extending between the biasing rails. A plurality of friction drivers are disposed on the conveying rail for only driving the tow bar extending between the trolleys on the conveying rail.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention is related to overhead mounted friction driveconveyor assemblies, and more particularly to overhead mounted frictiondrive conveyor assemblies for biasing a plurality of objects.

2. Brief Description of the Prior Art

Overhead mounted friction drive conveyor assemblies are widely used inautomobile assembly plants for moving objects, such as car doors,through a plurality of work stations on the assembly line. During thetypical assembly process of a vehicle, the doors are attached to thevehicle body and both components are painted together. Next, the doorsare removed from the vehicle body and placed onto the conveyor assemblyso that the vehicle body can be worked on without the doors in the wayand vice versa. Later in the assembly process, the car doors are removedfrom the conveyor assembly and re-attached to the vehicle body.

One problem with such an assembly process is that the friction driveconveyor assembly holding objects (e.g., in this case doors) in adirection parallel with the direction of motion can consume valuableconveyor line space. This is because typical friction drive conveyorassemblies do not have any way to efficiently store car doors.

For other types of conveyor assemblies, i.e. non-friction drive conveyorassemblies, conveyor assembly biasing has been used to offline car doorsand other objects. In biasing, the object being conveyed is angledrelative to the direction of motion, and thus, more space is providedalong the direction of motion to efficiently offline such objects.However, numerous design challenges have thus far prevented biasing frombeing used in friction drive conveyor assemblies.

There remains a significant and continuing need for an improved frictiondrive conveyor assembly for biasing objects such as car doors.

SUMMARY OF THE EXEMPLARY EMBODIMENT

According to one aspect of the invention, an overhead mounted frictiondrive conveyor assembly is provided including a conveying rail and abiasing rail. The conveying and biasing rails are spaced from oneanother and extend generally parallel with one another. The conveyorassembly also includes a carrier assembly having at least threetrolleys, a leading tow bar and at least one trailing tow bar. Theconveyor assembly further includes a biasing mechanism for guiding atleast two of the trolleys onto the biasing section of the conveying railand for guiding at least one of the trolleys onto the biasing rail. Aplurality of stationary friction drivers are disposed along the biasingsection of the conveying rail for moving said carrier assembly, and thestationary friction drivers are configured to only engage the leadingtow bar, which extends between the trolleys on the biasing section ofthe conveying rail. The trailing tow bars, on the other hand, areundriven and are pulled by the leading tow bar.

According to another aspect of the invention, the leading tow bar has afirst height, and the trailing tow bars have a second height which isless than the first height. In each carrier assembly, the bottoms of allof the tow bars are generally planar with one another, and therefore,the leading tow bar has driven portion which rises above the trailingtow bars. The friction drivers on the biasing section of the conveyingrail only engage the driven portion of the leading tow bar, andtherefore, the trailing tow bars pass underneath the friction driverswithout contacting the friction drivers.

An object, such as a car door, is attached to one of the trailing towbars. Since this tow bar extends between the conveying and biasing railsduring biasing, the object is angled relative to the direction of therails. Thus, adjacent carrier assemblies can be moved closer to oneanother, and the objects can be more efficiently stored, which allowsthe conveyor assembly to continue operating even if the objects cannotbe used immediately. The additional cost for this improved efficiency isminimized because the same type of friction driver can be used for boththe biasing and non-biasing sections of the conveyor assembly. In thenon-biasing sections, the friction drivers are positioned lower so thatthey can drive all of the tow bars. In contrast, in the biasingsections, the friction drivers are positioned higher so that they onlydrive the larger, leading tow bar.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages and features of the present invention will bereadily appreciated, as the same becomes better understood by referenceto the following detailed description when considered in connection withthe accompanying drawings wherein:

FIG. 1 is a schematic view of the exemplary overhead mounted frictiondrive conveyor assembly;

FIG. 2 is a cross-sectional view of an exemplary rail;

FIG. 3 is a side view of an exemplary carrier assembly supporting a cardoor;

FIG. 4 is a front view of an exemplary trolley disposed on a rail;

FIG. 5 is a front view of an exemplary friction driver in frictionalengagement with a trailing tow bar;

FIG. 6 is a schematic view of the biasing section of the exemplaryconveyor assembly;

FIG. 7 is a front view of an exemplary friction driver in a biasingsection of the conveyor assembly and in frictional engagement with aleading tow bar; and

FIG. 8 is a flow chart of an exemplary method of biasing objects on anoverhead mounted friction drive conveyor assembly.

DETAILED DESCRIPTION OF THE ENABLING EMBODIMENTS

Referring to the Figures, wherein like numerals indicate correspondingparts throughout the several views, an overhead mounted friction driveconveyor assembly 20 is schematically shown in FIG. 1. In the exemplaryembodiment, the conveyor assembly 20 is for moving car doors 22 througha predetermined path in an automobile assembly plant, and therefore, theobjects being moved by the conveyor assembly 20 are hereinafter referredto as car doors 22. However, it should be appreciated that the conveyorassembly 20 could be employed in a wide range of industries and could beused to move any desirable object, not just car doors 22.

The conveyor assembly 20 includes a conveying rail 24, generallyindicated, which extends through a predetermined path through theassembly plant. In the exemplary embodiment, the conveying rail 24extends through a paint zone 26 where freshly painted car doors 22 areplaced onto the conveyor assembly 20 to a final assembly zone 28 wherethe car doors 22 are removed from the conveyor assembly 20 and placed ona car body (not shown). The car doors 22 can be removably attached tothe conveyor assembly 20 with hooks, latches or any other desirableattachment mechanism. The conveying rail 24 also passes through a numberof work stations 30 for performing various steps in the assembly of thecar door 22 before it reaches the final assembly zone 28 and is attachedto the car body. For example, one of the work stations 30 could be forinstalling seals onto the car doors 22, and another of the work stations30 could be for installing a latching mechanism on the car doors 22.

Referring now to FIG. 2, in the exemplary embodiment, the conveying rail24 is mounted to the ceiling of the assembly plant and has an I-beamshaped cross-section with an upper horizontal member 32, a lowerhorizontal member 34 and a vertical member 36 extending between thehorizontal members 32, 34. It should be appreciated that the conveyingrail 24 could have any other shape including, for example, a tubularshape, a double channel shape or a T-shape. Referring back to FIG. 1,the conveying rail 24 can extend through straight sections, curves,inclines, declines or many other directions. The conveying rail 24 couldbe of one continuous piece or it could be composed of many pieces laidend to end along the predetermined path. The conveying rail 24 alsoincludes a biasing section 38 with a biasing rail 42 disposed adjacentthereto. However, as will be discussed in further detail below, duringnormal operation of the conveyor assembly 20, the biasing rail 42 is notused. It should also be appreciated that the conveying rail 24 could bemounted to any other overhead structure, i.e. not just a ceiling.

Referring now to FIG. 3, a car door 22 is removably attached to acarrier assembly 44, which transports the car door 22 along the rail 24.Each carrier assembly 44 includes a plurality of trolleys 46, 48, 50, 52interconnected with one another through a plurality of tow bars 54, 56,58. Referring now to FIG. 4, which shows an exemplary trolley 46, thetrolleys 46, 48, 50, 52 include at least two undriven rollers 60 whichengage the lower horizontal member 34 of the I-beam shaped rail 24 forsupporting the trolley on the rail 24. The undriven rollers 60 allow thetrolleys 46, 48, 50, 52 to roll along the rail 24, as will be understoodby those of skill in the art.

Referring back to FIG. 3, each carrier assembly 44 includes fourtrolleys 46, 48, 50, 52 defined serially as a leading trolley 46, asecond trolley 48, a third trolley 50 and a last trolley 52. Eachcarrier assembly 44 also includes a leading tow bar 54 extending betweenthe leading trolley 46 and the second trolley 48; a first trailing towbar 56 extending between the second and third trolleys 48, 50; and asecond trailing tow bar 58 extends between the third and last trolleys50, 52. The tow bars 54, 56, 58 are pivotally connected to the trolleys46, 48, 50, 52 in a manner known to those of skill in the art, andtherefore, the tow bars 54, 56, 58 can pivot relative to one another,for example, when the carrier assembly 44 is traveling through a curvedsection of the rail 24. In operation, the car door 22 is removablycoupled to the first trailing tow bar 56 of each carrier assembly 44. Itshould be appreciated that the carrier assemblies 44 could include anydesirable number of trolleys 46, 48, 50, 52 and tow bars 54, 56, 58.

As with conventional friction drive assemblies, the carrier assemblies44 are propelled along the conveying rail 24 by a plurality ofstationary and strategically positioned friction drivers 62. As shown inFIG. 5, each of the friction drivers 62 includes a generally U-shapedbracket 64 with a base 66 engaging the upper horizontal member 32 of theconveying rail 24 and a pair of legs 68 extending downwardly below theconveying rail 24. An electric motor 70 (or a similar type of actuator)is disposed on one of the legs 68 for rotating a driven wheel 72. Thecircumference of the driven wheel 72 is preferably of a high frictionmaterial for frictionally engaging the tow bars 54, 56, 58 of thecarrier assemblies 44 and applying a friction force thereon to propelthe carrier assemblies 44 along the conveying rail 24. An undriven wheel74 is coupled to the other leg 68 of the U-shaped bracket 64 formaintaining the friction contact between the tow bars 54, 56, 58 and thedriven wheel 72. The driven and undriven wheels 72, 74 are spaced fromone another by a gap which is sized similarly to the width of the towbars 54, 56, 58.

In operation, the tow bars 54, 56, 58 of each carrier assembly 44 passinto the gap between the driven and undriven wheels 72, 74, and frictionbetween the tow bars 54, 56, 58 and the driven wheel 72 propels thecarrier assembly 44 forward along the conveying rail 24. The frictiondrivers 62 are strategically positioned such that at any point along thepredetermined path, one of the tow bars 54, 56, 58 remains in contactwith at least one friction driver 62. The electric motors 70 of thefriction drivers 62 are in electrical communication with a controller(not shown), which individually controls the movement of each of thecarrier assemblies 44 on the predetermined path. The controller cancontrol the speed of the carrier assemblies 44 disposed on the rail 24and can stop the carrier assemblies 44, if desired.

In certain circumstances, it is desirable to store a number of car doors22 on the conveyor assembly 20. One such scenario is where the vehiclebody portion (not shown) of the assembly plant is disabled, but all ofthe work stations 30 along the predetermined path of the conveyorassembly 20 are functioning properly. Rather than shut down the conveyorassembly 20, it might be desirable to continue production and store thecompleted car doors 22 until the vehicle body assembly line returns tooperation. However, each carrier assembly 44 takes a length of conveyingrail 24 approximately equal to the lengths of the tow bars 54, 56, 58,and therefore, a limited number of car doors 22 can be stored along thelength of the conveying rail 24. To overcome this problem, the conveyorassembly 20 includes a biasing section 38 with a biasing rail 42 formore efficiently storing the completed car doors 22. As shown in FIG. 6,when biasing is desired, the car doors 22 in the biasing section 38 areangled relative to the direction of the conveying and biasing rails 24,42, and thus, the carrier assemblies 44 can be moved more closelytogether and the conveyor assembly 20 can continue operating until thebiasing section 38 is full.

The biasing section 38 includes the conveying rail 24 and a biasing rail42 extending in generally parallel relationship with one another.Referring back to FIG. 1, the conveying and biasing rails 24, 42 arejoined with the non-biasing portion of the conveying rail 24 in a pairof junctions 76. Each junction 76 includes a branching mechanism with apiece of branching rail 78 which is configured to pivot between a firstposition for guiding the trolleys 46, 48, 50, 52 onto or off of thenon-biasing section of the conveying rail 24 and a second position forguiding the trolleys 46, 48, 50, 52 onto or off of the biasing rail 42.The branching mechanisms are preferably electrically powered and are inelectrical communication with the controller, which controls thepositioning of the branching rails 78. When biasing is desired, thebranching rail 78 at the entrance of the biasing section 38 is held inthe first position until the leading and second trolleys 46, 48 havecleared the branching rail 78 and are on the biasing section of theconveying rail 24. Then, the controller operates to move the branchingrail 78 into the second position so that the third and last trolleys 50,52 are guided onto the biasing rail 42. The controller then quicklypivots back to the first position so that the leading and secondtrolleys 46, 48 of the next carrier assembly 44 are guided onto thebiasing section of the conveying rail 24.

The biasing rail 24 is spaced from the biasing section of the conveyingrail 24 by a distance which is less than the length of the firsttrailing tow bar 56. Thus, during biasing, the first trailing tow bar 56of each carrier assembly 44 is disposed at an angle a of greater thanninety degrees (90°) relative the leading tow bar 54. As will bediscussed in greater detail below, this configuration allows for onlythe leading tow bar 54 to be driven, and the leading tow bar 54 pullsthe undriven trailing tow bars 56, 58 along the biasing section 38. Asshown in FIG. 6, during biasing, adjacent carrier assemblies 44 are alsomoved closer to one another in the biasing section 38.

The friction drivers 62 on the biasing section of the conveying rail 24are configured to only engage the leading tow bar 54 of each carrierassembly 44 and to allow the trailing tow bars 56, 58 to passtherethrough untouched. As shown in FIG. 3, this is accomplished bysizing the leading and trailing tow bars 54, 56, 58 differently from oneanother. Specifically, the leading tow bar 54 of each carrier assembly44 has a first height and the trailing tow bars 56, 58 have a secondheight which is less than the first height. All of the tow bars 54, 56,58 are positioned such that their bottoms are generally planar with oneanother, and therefore, the leading tow bar 54 includes an upper portion80 which is disposed vertically above the tops of the trailing tow bars56, 58. Referring now to FIG. 7, the friction drivers 62 in the biasingsection 38 are positioned so that they only engage this upper portion 80of the leading tow bar 54. When the trailing tow bars 56, 58 approachthe friction drivers 62 in the biasing section 38, they simply passunderneath the driven and undriven wheels 72, 74 untouched.

FIG. 8 shows a flow chart for a method of biasing objects on an overheadmounted friction drive conveyor assembly 20. The method starts with thestep 100 of providing a conveying rail 24 and a biasing rail 42 spacedfrom and extending generally parallel to one another. The methodcontinues with the step 102 of providing a carrier assembly 44 includingat least three trolleys 46, 48, 50, 52, a leading tow bar and at leastone trailing tow bar. The leading tow bar 54 has a first height, and thetrailing tow bars 56, 58 have a second height which is less than thefirst height. The method then proceeds with the step 104 of driving witha friction driver 62 an upper portion of the leading tow bar 54 abovethe trailing tow bars 56, 58 so that the trailing tow bars 56, 58 passunderneath the friction driver 62.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings and may be practicedotherwise than as specifically described while within the scope of theappended claims. In addition, the reference numerals in the claims aremerely for convenience and are not to be read in any way as limiting.

1. An overhead mounted friction drive conveyor assembly comprising: aconveying rail; a biasing rail offset from and extending generallyparallel to said conveying rail; a carrier assembly including at leastthree trolleys, a leading tow bar and a trailing tow bar; and aplurality of stationary friction drivers disposed along said conveyingrail for moving said carrier assembly, wherein said stationary frictiondrivers are configured to only engage said leading tow bar and whereinsaid trailing tow bar is undriven.
 2. The friction drive conveyorassembly as set forth in claim 1 wherein said leading tow bar is largerthan said trailing tow bar.
 3. The friction drive conveyor assembly asset forth in claim 1 wherein said plurality of trolleys includes aleading trolley and a second trolley and a third trolley and a lasttrolley.
 4. The friction drive conveyor assembly as set forth in claim 3wherein said leading tow bar extends between said leading and secondtrolleys and wherein said trailing tow bar is a first trailing tow barextending between said second and third trolleys and further including asecond trailing tow bar extending between said third and last trolleys.5. The friction drive conveyor assembly as set forth in claim 4 whereinsaid leading tow bar has a first height and wherein said trailing barshave a second height being less than said first height.
 6. The frictiondrive conveyor assembly as set forth in claim 5 wherein the bottoms ofsaid trailing tow bars are generally planar with the bottom of saidleading tow bar such that said leading tow bar has an upper portiondisposed vertically above the tops of said trailing bars.
 7. Thefriction drive conveyor assembly as set forth in claim 6 wherein each ofsaid friction drivers on said conveying rail includes at least onedriven wheel positioned such that it engages only said upper portion ofsaid leading tow bar disposed vertically above the tops of said trailingtow bars.
 8. The friction drive conveyor assembly as set forth in claim1 wherein said biasing rail is spaced from said conveying rail adistance which is less than the length of said tow bars.
 9. The frictiondrive conveyor assembly as set forth in claim 1 wherein each of saidfriction drivers includes at least one driven wheel and at least oneundriven wheel.
 10. The friction drive conveyor assembly as set forth inclaim 9 wherein said driven and undriven wheels of said friction driversare spaced from one another by a gap sized similarly to the width ofsaid tow bars.
 11. The friction drive conveyor assembly as set forth inclaim 10 wherein each of said friction drivers includes a U-shapedbracket and wherein said undriven wheel is coupled to one leg of saidU-shaped bracket and wherein said driven wheel is coupled to another legof said U-shaped bracket.
 12. The friction drive conveyor assembly asset forth in claim 11 wherein said driven wheel is coupled to anelectric motor.
 13. The friction drive conveyor assembly as set forth inclaim 1 wherein said conveying and biasing rails each have an I-shapedcross-section.
 14. The friction drive conveyor assembly as set forth inclaim 1 wherein said conveying rail includes a biasing section and anon-biasing section.
 15. The friction drive conveyor assembly as setforth in claim 14 where said biasing rail is joined to said conveyingrail through a pair of biasing mechanisms each including a branchingrail.
 16. (canceled)
 17. The friction drive conveyor assembly as setforth in claim 15 wherein said non-biasing section of said conveyingrail includes a plurality of friction drivers spaced farther from oneanother than said friction drivers on said biasing section of saidconveying rail.
 18. A method of biasing objects on an overhead mountedfriction drive conveyor assembly, comprising the steps of: providing aconveying rail and a biasing rail spaced from and extending generallyparallel to one another; providing a carrier assembly including at leastthree trolleys and a plurality of tow bars extending between andinterconnecting the trolleys; selectively guiding at least one trolleybut not all of the trolleys onto the biasing rail such that at least oneof the tow bars extends parallel to the conveying rail and at least onetow bar extends between the conveying and biasing rails; and drivingonly the tow bar parallel to the conveying rail with a friction driver.19. The method as set forth in claim 18 wherein the plurality of towbars include a leading tow bar having a first height and at least onetrailing tow bar having a second height and wherein the first height ofthe leading tow bar is greater than the second height of the trailingtow bar.
 20. The method as set forth in claim 19 wherein the step ofdriving the tow bar with the friction driver is further defined asdriving only an upper portion of the leading tow bar disposed above thetrailing tow bar so that the trailing tow bar passes underneath thefriction driver.